// https://www.acwing.com/problem/content/792/

#include <iostream>
#include<iomanip>
using namespace std;


double solution(double v) {
    double left = -10000;
    double right = 10000;
    while (right - left >= 1e-7) {
        double mid = (right + left) / 2;
        double y = mid * mid * mid;
        if (y >= v) {
            right = mid;
        } else {
            left = mid;
        }
    }

    return left;
}


int main() {
    double v;
    cin>>v;
    cout<<fixed<<setprecision(6)<<solution(v)<<endl;
    return 0;
}

